Polyaromatic hydrocarbons (PAH) are environmental pollutants that require metabolic activation to exert their toxic effects. One pathway of activation is via the formation of trans-dihydrodiols to yield diol epoxides which alkylate DNA. Trans-Dihydrodiols are also converted to omicron-quinones via an alternative pathway mediated by dihydrodiol dehydrogenase (DD). By diverting trans-7,8-dihydroxy-7,8- dihydrobenzo(a)pyrene (BP-diol) down this pathway, benzo(a)pyrene-7,8- dione (BPQ) is produced. Two possible consequences of this pathway are: 1) The formation of BPQ prevents BP-diol from being converted to benzo(a)pyrene-trans-7,8-dihydrodiol-9,10 epoxide (BPDE). The consequence would be detoxification; 2) BPQ can undergo covalent binding to DNA or redox cycle to generate reactive oxygen species (ROS) which can oxidatively damage DNA bases. The consequence would be activation. Establishing the role of the DD in PAH metabolism has been hampered by the reactivity of the omicron-quinone product and competing pathways of trans-dihydrodiol metabolism. Stable transfection of the cDNA of rat liver DD into single cell lines known to metabolize PAH but limited in DD-related biotransformation would provide insight into the contribution of DD to PAH metabolism. By exposing control and transfected cells to BP-diol, the influence of DD on the overall metabolism of BP-diol will be determined. The ability of reactive metabolites (BPDE or BPQ) to form covalent DNA adducts in stable transfectants exposed to BP-diol and the concommitant changes in redox stat will be assessed. The formation of ROS in stable transfectants treated with BP-diol will be measured. Indirect oxidative damage of DNA that results from the formation of BPQ in stable transfectants will be measured by detection of 8'-hydroxy- deoxyguanosine and the incidence of DNA strand breaks.